Servomotor



Nov. 9 1948. c, A. NERACHER arm. 2,453,156

BY 1448 1121:) 7' an);

A okmna Nov. 9, 1948.

Filed Nov. 13.,

nan 5 C. A. NERACHER ETAL SERVOIOTOR i stants-Sheet. 4

12: 12/ H lip v 11v VENTORs ATTORNEK.

Patented Nov. 9, 1948 i UNITED STATES PATIENT OFFICE- SERVOMOTOB Carl A.Neracher and William '1. Dunn, Detroit,

Mich, asslgnors to Chrysler Corporation, Highland Park, Mich, acorporation of Delaware Application November 13, 1939, Serial No.304,060

8 Claims. 1

This invention relates to power transmissions and refers moreparticularly to improvements in speed ratio changing mechanismespecially adapted for use in driving motor vehicles.

The principal object of the invention is to provide an improved speedratio changing mechanism for driving the propeller shaft of a motorvehicle at a speed dliierent from, and preferably faster than, thedriving shaft thereof.

Additional objects of our invention are to provide a mechanism of theaforesaid character having improved characteristics of long life,quietness of operation, automatic response to vehicle travel, and lowmanufacturing cost.

More specifically, another object of the invention is to provide anoverdrive transmission mechanism which incorporates an overrunningclutch action between the driving and driven shafts during normaldriving for synchronizing the two shafts preparatory to establishing ofthe faster drive, but which does not permit continuous overrunningduring normal drive as is the case with conventional devices of thistype, and which requires no lockout means for reverse drive.

Another object is to provide an improved overdrive mechanism wherein theplanet pinions do not rotate during direct driving and the annulus gearis driven at direct drive speed rather than at overdrive speed. Such anarrangement results in much quieter operation due to elimination of"gear sing in direct drive, and promotes economy by cutting down 011churn in the overdrive casing.

Still another object is to provide an improved means for clutching thereaction element of the overdrive planetary gear train to the casingwhereby the same clutching means may be used for initially establishingthe overdrive, for quickly dis-establishing the overdrive by kickdown"action of the accelerator pedal or other control means and forre-establishing the overdrive after kickdown.

A further object is to provide an improved means for controlling theoperation of the overdrive unit wherein engine vacuum may be' used underthe control of a solenoid which also. acts to lock the clutching meansin overdrive position, thus avoiding the possibility of unintentionaldisengagement of the clutch due to a low vaccum- 2 fast drive is urgedto its engaged position by vacuum and to its disengaged or kickdownposition by a spring; the engagement and disengagement of said pawlbeing controlled by a solenoid which also acts to lock the pawl in itswaged position upon establishment of the fast drive.

A still further feature is the provision of a novel system of switchesfor grounding of the engine ignition for kickdown, the said switchesbeing so arranged that ignition grounding may occur by reason ofaccelerator pedal overtravel only when the overdrive mechanism is inoperation.

An additional and extremely important feature of our invention residesin the provision of a double over-running clutch device which eliminatesfree-wheeling of the vehicle in all speeds in addition to eliminatingthe necessity for locking out the overdrive mechanism during reversedriving as is the case with overdrives of the prior art. Ln connectionwith the double overrunning device, we have provided improved blockermechanism which positively prevents engagement of the planetary reactionelement locking pawl except during coast of the vehicle, the blockingelement being moved out of blocking position by action of the planetaryunit itself during coast of the vehicle.

In our oopending divisional application Serial No. 433,544, filed March6, 1942, we have included claims directed to our speed ratio changemechanism and system of control therefor. In the subject application wehave included claims directed to our novel servo-motor embracing ournovel compact arrangement of controlling and controlled parts comprisinga unit motor structure, the principles of which are best illustrated inFigs. 5 and 7.

Additional objects and advantages of our invention will be more apparentfrom the following detailed description of a. preferred embodimentthereof, reference being had to the accompanying drawings in which:

Fig. 1 is a partial side elevational view of a motor vehicle equippedwith the improved overdrive mechanism showing the essential controlapparatus.

Fig. 2 is a diagrammatic representation of the vehicle drive mechanism.

Fig. 3 is an enlarged sectional view of the lost motion connectionbetween the throttle valve control lever and the accelerator pedallinkage. Fig. 4 is a'sectional view in side elevation of the improvedoverdrive mechanism, part of the regular vehicle transmission also beingshown.

Fig. 5 is a sectional view taken approximately along the line 5-5 ofFigs. 1, 4 and 6.

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 5.

Fig. 7 is a sectional view taken along the line 1-1 of Fig. 5.

Fig. 8isasectionai viewtaken along theline 8-8 of 1'18. 4.

Fig. 9 is a circuit diagram of the electrical connections.

Fig. 10 is a sectional view of the governor mechanism for controllingthe cut-in of the overdrive mechanism.

R18. 11 is a sectional view along the line I l-l I of Fig. 10.

Referring to the drawings in which like reference numerals designatecorresponding parts in the following description, we have illustrated(Fig. 2) our overdriving mechanism D interposed between a speed ratiotransmission C of the manually controlled type and a driven shaft ii,the latter extending rearwardly to drive the rear wheels H through theusual differential mechanism l2. The transmission C is connected to theengine A through the usual clutch B operated by a pedal I8, and isadapted for selective control by the driver by means of the links (4,IS, the lever i6 and the Bowden cable H, the links and cable beingactuated by a control lever (not shown) mounted at the top of thesteering column.

The transmission C may be of general conventional construction andoperation thus we' have shown only a part of it in Fig. 4 wherein i8designates a low speed and reverse gear adapted to be shifted by theusual selector control member forwardly (to the left as viewed in Fig.4) into mesh with the low speed countershaft gear 20, or rearwardly intomesh with the reverse idler gear 2i. The latter is in constant mesh withthe countershaft gear 22. The intermediate speed gear 23 journaled onthe mainshaft is in constant mesh with the countershaft gear 24 and maybe clutched to the shaft 25 for driving the same at an intermediatespeed by means not shown, it being understood that by propermanipulation of the transmission controls, the mechanism may be adaptedto selectively produce reverse drive and different speed ratio drivesforwardly.

In Fig. 4, the shaft 25 is supported at the rear end of the transmissioncasing 26 by an antifriction ball bearing 21 and has a reducedrearwardly extending portion 28 with which the overdrive mechanism isoperatively associated. The overdrive is housed in a casing 29 securedto the casing 25 by fasteners 30 and carries an antifriction bearing 3!at the rear end thereof in which is supported a tailshaft 32. The latterhas a hub member 33 splined thereto which carries the drum 34 of atransmission shaft brake referred to generally by the numeral 36 inFig. 1. A fiber seal forms a grease retainer for the end of the housing.

The tailshaft 32 has an enlarged bell-shaped forward portion 31 whichcarries the annulus gear 38 of theplanetary gearset, the drivingconnection therebetween being provided by the teeth 29. A snap ring 40retains gear 38 in correct position. In mesh with the annulus gear 88 isa plurality of planet gears 4| rotatably mounted on a carrier 42 bymeans of axles 48. The carrier is splined at 44 on the end of the shaftportion 28 and is separated from the part 31 by a suitable bushing 45.

The planet gears 4| also mesh with a sun gear 46 journaled on the shaft28 at 41 just forwardly of the carrier 42. The sun gear has a forwardlyextending control sleeve 48 provided with a plurality of slots 48, thepurpose of which will be presently made clear. The sleeve 48 is providedwith an external cam 48 and an internal cam 88 which respectively formdrive elements of outer and inner overrunning devices having sets ofrollers designated II and 82 respectively. The other drive element ofthe inner overrunning device consists of a cylindrical member 83 splinedon the shaft 28 at 84. The other drive element of the outer overrunningclutch consists of a member II provided with a cylindrical inner surfaceand a toothed outer surface; the teeth 88 of which are adapted to bereceived into slots 81 milled into the inner surface of the casing 28.It will be noted (Figs. 5 and 8) that the slots are longer than theteeth ii the clearance thereby provided permitting the member 88 aslight degree of rotational movement about the axis of the assembly. Aspring 58 disposed in a slot 8| cut in the easing 28 and fixed againstmovement relative to the casing and to the member 58 at 89 and 88respectively acts to urge the member 88 to'the limit of its rotationalmovement in the direction of forward rotation of the shaft 28, as shownin Fig. 8.

The overrunning rollers 8i and 82 are carried by a common cage orcarrier 82 having spokes 63 (see Fig. 5) which extend through the slots48, three of said slots being cut deeper, as shown in Fig. 4, toaccommodate the same.

The cage 82 maintains the rollers Si, 82 in a definite relation withrespect to each other and with respect to the cams 48 and 88. From Fig.8 it may be seen that the rollers 8| are advanced circumferentially inthe direction of rotation of the shaft 28 relatively to the rollers 82and the cams 49 and 58 are so related to the rollers that the rollers 5!are in their neutral position when the rollers 52 are locked in drivingposition. Conversely, movement of the cage 63 to lock the rollers ii indriving position will move the rollers 52 into their neutral non-drivingposition.

From the description so far, it may be seen that forward (clockwise)rotation of the shaft 28 will also rotate the planet carrier 42, theannulus 38 being held stationary due to the resistance of the rear drivewheels II to which the annulus is directly connected. This will causethe sun gear 48 to be driven forwardly at a greater speed than that ofshaft 28, which in turn will cause the sun gear control sleeve 48 todrivingly engage the member 58 through lock-up of the rollers 82 betweenthe cam and the outer cylindrical sur-- face of the member 83. Theentire planetary gearset will then rotate as a unit and drive thetailshaft 2: at the speed of the shaft 28, the sleeve 48 rotating freelyrelatively to the reaction member 58 through overrun of the rollers 8|.Under such conditions the positions of the various parts are as shown inFig. 8 and the vehicle is driving in direct or conventional gear. If thedriver removes his foot from the accelerator pedal permitting thevehicle to coast, the annulus 28 will become the driving element of theplanetary set and the direction of rotation of the planet gears 4| willbe reversed thus causing the sun gear 48 to rotate backwardly(counterclockwise) and disengage from-driving relationship with themember 58 thereby unlocking rollers 82 which may then roll freely andlocking the rollers ll between the cam 48 and the member 88. The latterthen becomes the reaction taking element for the planetary set and theshaft 28 is driven forwardly at a reduced speed relatively to shaft 82.It is therefore apparent that free-wheeling cannot occur when the car isin conventional gear.

When the transmission C is set for, reverse drive, shaft it rotatesbackwardly (counterclockwise) and the resistance on the annulus ll atthe start causes the sun gear 40 to be rotated rearwardlv therebylocking to the member II. The annulus II will then be driven backwardlydriving the tailshaft If backwardly at a speed greater than that of theshaft ll. In other words, the drive in reverse is an overdrive. theeffective ratio of which may be adjusted as desired by suitablyproportioning the gears 2| and 22.

Upon deceleration in reverse. the annulus a will reverse the rotation ofthe planet pinions 4| and cause the sun gear 40 to unlock from themember 55 and lock up to the member 43 thereby driving the shaft 28 atthe speed of the tailshaft 32. I

During the above described operations, the reaction taking element 55will rotate backwardly against the spring it whenever lock-up occursbetween the members 48 and 55 thereby cushioning the shock occasioned bythe reversal of the sun gear.

It is to be noted that the aforesaid arrangement provides a decidedadvantage when rocking the vehicle between forward and reverse, as isfrequently done when the car is mired. because a short period offree-wheeling occurs during reversal of the sun gear and a'fast shiftmay be obtained without use of the clutch pedal.

Means will now be described for holding the sun gear 46 against rotationduring forward driving of the vehicle to furnish reaction for theplanetary gearset to provide a forward overdriving ratio and forcontrolling the holding means to provide desirable and convenientcontrol thereof.

Referring now to Figs. 5,6 and 7, in conjunction with Figs. 1 and 4, itmay be seen that the end wall 64 which separates the casing from thecasing 28 has mounted on the left side thereof a motor unit referred togenerally as 85. This motor unit comprises a vacuum cylinder 66 having adifferential pressure operated member ment II and the bottom of the cu'l'l upon movement of the rod to engage the pawl. The vacuum actuateddiaphragm 41 is also provided with a coil spring ll. suitably retainedin place by cups "4 which tends to urge the diaphragm n and the rod lloutwardly. The spring ll is also adapted to be compressed when vacuum isadmitted to'the cylinder 66 to move the rod 4| inwardly.

Between the cylinder 8! and the part 84 a valve housing II is providedwhich has an electrical solenoid ll attached to the bottom side thereof.The solenoid is provided with the usual coil l2 and plunger II, thelatter having an upwardly extending portion 84 which is adapted uponenergization of the solenoid to engage the reduced portion 85 of the rod68 to thereby lock the latter against unintentional outward movementunder the influence of springs 15 and II due to a low vacuum conditionwhich might exist in the cylinder 6 because of high torque demand or thelike.

' 'The valve housing 80 is provided with a chambeing open to theatmosphere at 9!.

herein illustrated in the form of a diaphragm I1 therein operativelyassociated with thrust-transmitting means in the form of a rod 88 whichextends transversely inwardly of the wall 64 and which has a pawl 68secured to the end thereof by means of a ball connection It.

The 'pawl 89 is provided with a notch H which is adapted to engage theforwardly extending ledge I2 of the reaction taking member when thelatter is in its forward position, this being the position shown inFigs. 5, 6 and 8 and the one The solenoid plunger rod portion 84 has areduced portion at 92 to which is secured a fiber valve member 91, thelatter being adapted to seat on top of the annulus member 94 when thesolenoid is de-energized thereby cutting oil the vacuum or low pressurechamber 8'5 from comrhunication with the main chamber 88 and the motor86. The rod 84 is further provided with a stirrup-like member 95fastened thereto by a pin it. This member 95 carries an upright pin 91on which is disposed a valve member 98 of fiber or the like whichisurged upwardly by a coil spring 0!.

to which the member 55 is urged by the spring S8. The member 55 thusacts as a blocker member for preventing engagement of the pawl 68 duringthe time that the sun gear 4! is locked to the shaft 28 by the rollers52. The ledge 12 is provided with a milled slot 13 which, upon rotationof the member 55 rearwardly to take up the clearance between the slots51 and the teeth 56, will permit the pawl to pass through and engage inthe slots 49 of the sun gear control sleeve 48.

The valve member 88 is adapted to cut off the entrance of atmosphericair into the valve cham-' ber 88 upon energization of the solenoid 8|which action, of course, causes the plunger 83 to move upwardly liftingthe valve 83 oil its seat and admitting vacuum into the chamber 88whereupon the air present in cylinder 86 on the left side of thediaphragm 6'! is exhausted and the atmospheric pressure on the otherside of the diaphragm causes the diaphragm to move inwardly toward theleft to engage the pawl as in one of the slots 4! provided that the pawlis unblocked. The extreme upper end of the rod portion 84 engages therod Bl just forwardly of the reduced portion upon upward movement of thesolenoid plunger. Inward movement of the rod 68 to engage the pawl willbring the reduced portion 85 adjacentv the end of rod portion 84whereupon the plunger II will move upwardly an additional amount toengage the rod portion 84 in the notch 05, thus locking the rod Iagainst movement in the outward direction under the influence'of thecoil springs 15 and 18, which action might occur under conditions of lowvacuum, such as when the vehicle is ascending a hill at low speed. 7 Thevalve member 0! seats against the opening in the plug shaft 32.

7 I and cuts off the atmosphere during the first part of the movement ofplunger 00, the second part of said movement being accommodated byyielding of the spring 00.

Novel means is provided for controlling the energization oi the solenoid0i to cause the pawl 00 to be engaged under the proper conditions ofvehicle operation and for returning the drive to conventional gear bydisengagement of the pawl under all conditions of vehicle operation asdesired by the driver.

In Fig. 4 a worm IN is shown keyed to the tail- This worm drives thevehicle speedometer (not shown) and in addition drives a governormechanism for controlling the speed at which the solenoid 0I isenergized for engaging the overdrive mechanism. The governor, referredto in Fig. 10 by the numeral I02, is mounted on the far side of thetransmission casing 20 by means of a boss I03 and includes a shaft I 04having a worm gear I05 formed thereon for engagement with the worm IN.The shalt turns in a bushing I08 and has an enlarged cup-shaped upperportion I01. A setscrew I00 engages a groove I09 cut in the shaft forretaining the same in correct position. A pair of centrifugally actuatedweights IIIl, III are pivoted in the cup I01 at H2, H3 respectively andare normally urged toward one another by a coil spring I24, an upwardlybowed flexible element I I4 being attached to each of said weights asshown in Figs. 10 and 11. The element H4 has an upwardly extending postI I5 attached thereto which extends upwardly through an insulating stripI I! into contact with a switch arm I IS. The latter is pivoted at I I0to a cover H9 and has a contact I at one end which is adapted to engagea second contact I2I carried by the insulating strip II'I upon rotationof the shaft IM at a speed suflicient to cause the weights IIIl, III tomove outwardly away from each other appreciably. The contact I2I isconnected to one side of the solenoid 8i (Fig. 9) by a wire I22 and theswitch arm H6 is connected by a wire I23 to ground.

The spring I24 may be of any desired strength to give the cut-incharacteristics desired for the overdrive. It has been found preferableto provide a spring of such strength that the contact I20 will engagethe contact I2I to close the solenoid circuit at a vehicle speed ofapproximately 20 miles per hour at which time the driver may eilect ashift to overdrive ratio by momentarily releasi. g the accelerator pedalwhich will reverse the torque through the transmission and unblock thepawl 69 as will be more clearly explained later on herein.

Once the pawl 69 has been engaged by action of the vacuum motor 66, itwill remain engaged so long as the solenoid 8i is energized, which, asaforesaid, occurs at approximately 20 miles per hour. We have, however,provided means under the direct control of the driver for de-energizingthe solenoid and effecting a quick shift back to direct drive at speedsgreater than 20 miles per hour. This means is entirely separate from thegovernor mechanism and is controlled by overtravel of the regularvehicle accelerator pedal. The mechanism for securing this function ispreferably arranged so that the accelerator pedal may be depressed toovertravel the engine throttle when fully open to thereby efiect adeenergization of the solenoid and a momentary interruption of theengine torque to permit withdrawal of the pawl 69 from engagement withthe sun gear 46. This arrangement is termed a kickdown" con- 8 trol, andis preferably associated with the accelerator pedal since the driverordinarily has his loot on this pedal and naturally depresses the pedalwhen increased power or speed is desired. The kickdown control ispreferably used to secure increased torque when a quick increase invehicle speed is desired such as when passing another car on a hill.

ReferringtoFigs.1 and0,itmnybeseenthat the accelerator pedal I20 isconnected to the throttle control member I20 to a lost motion mechanismgenerally referred to at I" and which is shown in detail in Pig. 3. Theaccelerator pedal I20 is operatively connected by means of a link I20with a lever I20 pivoted on the vehicle at I00. The lever I20 is in turnconnected throuth the throttle valve control lever I20 by means of a rodIOI which is adapted to slide through an opening in the ear I02 of abracket I00, this bracket having a forward portion I04 secured to aguide block I00 provided with a rearwardly open bore I00 and havingpivotal connection at I01 with the throttle valve control lever I20. RodIOI has fixed thereto a collar I00 forwardly adjacent the ear I02, apreloaded spring I00 surrounding the rod and acting between the blockI05 and the collar I00 so that normally this spring serves as aconnection between the rod IOI and block I05. The spring I00 functionsas an overtravel spring and permits rod IOI, lever I20 and pedal I20 tohave a certain amount of overtravel after the throttle valve controllever I20 has engaged the stop I40 provided on the carburetor device asshown in Fig. 1. During overtravel of the accelerator pedal I20, springI 00 advises the driver that he is manipulating the accelerator pedalfor actuation of the kickdown mechanism by reason of the extraresistance in addition to the regular accelerator pedal return springIll aflorded by this compression of spring I00 which occurs when thecollar I00 moves toward the block I35. In other words, when theacceleratcr pedal is manipulated for kickdown, extra resistance isencountered by reason of compressing spring I09 during operation of theFig. 3 mechanism which accommodates overtravel oi the accelerator pedalbeyond its wide open thrott'le position. The forward end of rod IOI isslidably disposed in the bore I 00, the bracket I04 limiting theoperating tendency of the rod IOI and block I00 under the action ofspring I00.

when the accelerator pedal I20 is depressed to open the throttle valvewhich is indicated at I42 in- Fig. 1, link I20 operates to swing thelever I29 forwardly about the pivot I00, rod IOI thrusting block I00forwardly with the relative movement therebetween so as to swing leverI20 forwardly and, as the accelerator pedal is depressed to the end ofits range of throttle opening movement, the lever I20 will engage thestop I40. The accelerator pedal I25 is then adapted to have a furtherrange of movement which overtravels the throttle valve, whilemaintaining the latter in its wide open throttle position, and in orderto accommodate this overtravelling movement, the mechanism illustratedin Fig. 3 comes into action so that during said overtravel of rod I 0|,said rod will slide into the bore I00 and compress spring I 00 with theforwardly moving block I05 or the throttle operating lever I20. Uponrelease of the accelerator pedal I20, spring I00, assisted by spring I,operates to restore the parts to their normal closed positionillustrated in Fig. 1. During this return movement of the parts, rod HIand its associated parts, including accelerator pedal I20, move relativeto block I00 and lever I26 until the collar I36 engages the ear I32 ofthe bracket I34 and thereafter spring I M will move rod I3I along withblock I35 and lever I26 without lost motion until the throttle valve I42is restored to closed position and the accelerator pedal I25 iscorrespondingly positioned as in Fig. 1.

The aforesaid overtravelling movement of accelerator pedal I25 isadapted to effect energization of the solenoid 6| through operation of aswitch I43. A switch operating lever I44 is fixed to the aforesaid leverI29 and is adapted to move therewith, this lever I44 having a pair ofswitch operating fingers I45 and I46 alternately engageable with theswinging operating element I41 of switch I43 which is preferably of thewell-known snap-over type and provided with terminals I46 and I49.Terminal I46 is connected by a wire I56 which is grounded on the vehicleframe (Fi 9) and terminal I49 is connected by a wire II toone side of arelay I52, the latter being in turn connected by a wire I53 to one sideof the vehicle ignition switch I54.

In the fully released (throttle closed) position of the acceleratorpedal I25 as is shown in Fig. 1,

the finger I46 has operated the switch element face of switch elementI41. .When the accelerator I pedal is depressed for the aforesaidovertravelling range of movement, the finger I45 then swings the switchelement I41 in a counterclockwise direction to cause this element tohave the well-known snap-over action in closing the switch I43. When theaccelerator pedal is again partially released to its wide open throttleposition, finger I46 does not immediately engage switch element I41 forrestoring the switch to its open position, this finger I 46 preferablyengaging the switch element when the pedal nears the end of its movementto fully released position such that the last portion of the releasingmovement of the pedal is utilized for causing finger I46 to efiect thesnap-over switch opening movement of the element I41 in restoring theparts to their Fig. 1 position.

Thus it may be seen that the switch I 43 when closed will effectenergization of relay I52, one side of said relay being connected toground throu h wire I5l and switch I43, and the other side of said relaybeing connected through'wire I53. ignition switch I54, wire I55, vehicleammeter I55. wire I51 and wire I56 to one side of the vehicle batteryI59 which is in turn grounded through wire I66. The contacts I6 I, I62of the relay I52 are normally closed thus connecting one side of thesolenoid 8| to the battery I59 through the wires I63 and I64. It maythus be seen that closing of the switch I43 will open the contacts I 6I.I62 thus tie-energizing the solenoid 6|. In addition. the switch I 43will eflect a momentary grounding of the vehicle ignition for securingthe toruue reversal necessary to unload the pawl 69 to thereby permitthe springs and 16 to pull the nawl out of engagement with the sun gearontrol sleeve 46. It may be seen from Fig. 9 that the wire I64 connectsone side of the switch I43 with an ignition interrupter control. switchI65 which is-connected in series through wire I66 with r. secondignition interrupter control switch I61, the latter switch beingconnected through a wire I68 with the ignition coil I69 and thedistributor I16. A jumper wire-I1I connects the coil I69 and distributorI16 with the wire I53 which is con- 10 nected through the ignitionswitch and ammeter to one side of the vehicle battery I59.

The diagram of Fig. 9 also shows a switch I12 which is adapted to bemounted on the instrument panel of the vehicle as indicated in Fig. lfor manual operation by the driver. The switch I12 is ordinarily closedbut may be opened by the driver to cut out the overdrive mechanism ifany way effecting the operation of the overdrive mechanism, the use ofsuch switch being optional in cases where it is desired to prevent shiftof the transmission into overdrive ratio until after the vehicle hasbeen shifted into direct drive ratio in the manually shiftabletransmission mechanism C.

Referring to Fig. 5 it may be seen that the switch I65 includes ahousing I15 which encases a pair of relatively fixed contacts I16, I11which are connected to the wires I66, I64, respectively, and a movablecontact member I16 urged by a spring I19 into switch closing contactwith the fixed contacts I16, I11. The movable contact member I16 isprovided with an actuating pin or plunger I66 which has a lost-auctionoperating relationship with red 66 such that the pin I66 15- adapted tobe engaged by the outer end of the rod 66 when the parts are in theposition shown in Fig. 5, thus maintaining theswitch I65 in openposition to break the circuit between the wires I64 and I66.

The switch I61 is generally similar in construction to switch I65 exceptthat the spring l6l thereof urges the plunger member I62 out of contactwith the contacts I63, I64, the said plunger having an actuating pin I65which is adapted to be engaged by the lower end of the solenoid plunger63 to close the switch I61 when the, parts are in their Fig. 5 position.

It may thus be seen that when the vehicle is being driven in direct orconventional gear, the switch I65 is open and the switch I61 is closed.Under such conditions. if they accelerator P dal I25 should be fullydepressed to the limit of its overtravel position, grounding of theignition could not take place due to the interruption in the ignitiongrounding circuit at the switch I65. Upon shifting of the mechanism intooverdrive speed ratio, upward movement of the solenoid plunger 63 opensthe switch I61 and the subsequent inward movement of the pawl actuatirod 66 permits the switch I65 to close. Under these conditions, upondepression of the accelerator pedal to the limit of its overtravelposition which will of course effect closing of the switch I 43 anddeenergization of the solenoid 6| under operation of the relay I52,return of the solenoid plunger I83 to the Fig. 5 position will closeswitch I61. Switch I65 being also closed, this will effect the groundingof the ignition through wires I56, switch I43, wires I5I, I64, switchI65, wire I66, switch I61 and wire I66. At, the instant the ignition isgrounded, a reversal of torque through the transmission will occur whichwill unload the pawl 69 permitting the springs 15 and 16 to thrust thediaphragm 61 and rod 66 outwardly disen- 11 I85 after rod 68 anddiaphragm 51 have moved outwardly sufficiently to take up thelost-motion between rod 68 and pin I80 and thus open the switch againstthe action of the biasing spring I thereby interrupting the ignitiongrounding circuit and restoring the ignition.

The kickdown operation Just described takes place in an instant and themomentary interruption of the ignition circuit is barely noticeable tothe occupants of the vehicle. As soon as the ignition circuit isrestored by the opening or the switch I55, the motor drives under wideopen throttle conditions in direct drive until the accelerator pedal ispartially or fully released. It is not necessary for the driver to holdthe accelerator pedal I f-ully depressed to the full extent of itsoven-travel in order to maintain the vehicle in kickdown because thesolenoid 8| will remain deenergized until the pedal I25 hassubstantially returned to its idle position under the influence of thespring Ill. This is necessary because of the construction of the switchcontrol lever I which is explained above, it being necessary that theaccelerator pedal I25 be substantially returned to its idle positionbefore the finger I will contact the element I 61 of the snap-overswitch I.

In the operation of the overdrive mechanism as a whole. let it beassumed that the switch I1! is included in the overdrive control circuitand that the vehicle is at rest with the engine running. The manuallyoperable change speed mechanism C may be manipulated and the vehicleaccelerated through the gears therein until direct drive through thetransmission mechanism C has been obtained. During this period a speedgreater than that necessary to effect closing of the governor switchcontacts I26 and I 2| may be obtained but energization of the solenoid8| will not occur until direct drive has been obtained whereupon theswitch I12 will be closed by engagement of the high gear rail of thetransmission C with the element I" of the switch. After a speed not inexcess of approximately 20 miles per hour has been reached in high ordirect drive, the contacts I20 and I 2| of the governor controlledswitch will close thus effecting energization of the solenoid II whichwill cause the plunger 82 thereof to thrust upwardly until the upper endportion 84 engages the rod 88 Just inwardly of the depressed portion 25thereof. A spring III will open the switch I61 at this time. The upwardmovement of the solenoid plunger 82 will unseat the valve element 62thereby admitting vacuum from the intake manifold of the vehicle enginewhich is present in chamber 86 into the main valve chamber ll. At thesame time the valve element 58 will be seated against the opening in thepart III to cutofl the admission of atmosphere into the valve chamberI88. The air in front of the diaphragm 61 of the motor 65 will thus beexhausted and the diaphragm will tend to move inwardly toward the shaft28 but is prevented from doing so by the engagement of the blocker ledgeI2 with the notch ll of the pawl 69.

The driver may then secure a shift into overdrive ratlo by momentarilyreleasing the accelerator pedal I25 which will cause the sun gear 26 todisengage from the rollers 52 and rotate rearwardly into drivingengagement with the rollers 5| to thereby pick up the element 55 androtate it rearwardly against the spring 58 to take up the clearancebetween the teeth 56 and slots 51. This backward movement of element 55will unblock the pawl '69 thereby permitting the pawl to be thrustinwardly by the diaphragm 61 and rod 6;

12 into engagement with one of the slots ll. It should be noted that atthis particular instant the sun gear control sleeve 46 is stationarybecause of the reverse rotation of the planet gears 4| therebypermitting the pawl 52 to engage the slots 49 smoothly and silently. Ifit should happen that th sleeve 46 is in such position that the pawl 69cannot engage one of the slots thereof, the engagement will occurinstantly while depressing the accelerator pedal to continue driving ofthe vehicle. As may be seen from Fig. 5 the pawl II is inclined on itsforward face at I" and the sleeve 46 is chamfered at I" adjacent each ofthe slots 48 to facilitate engagement of the pawl 66 should said pawlfail to engage while the sun gear is stationary.

Inward movement of the diaphragm 61 and rod 68 will of course permit thespring I'll to close the switch I65. The driver may then depress theaccelerator pedal and the car will be driven forwardly in overdriveratio.

The car will continue to be driven in overdrive ratio so long as theaccelerator pedal I25 is not depressed to the limit of itsovertravelling range of movement and the speed of the governor mechanismI02 which in the particular embodiment being described is preferably setat approximately 20 miles per hour. If the speed of the vehicle isallowed to fall substantially below 20 miles per hour, the weights Illand III of the governor mechanism will be moved toward each other by thespring I24 thereby lifting the movable switch element III and operatingthe contacts I26 and I2 I. The solenoid II will thus be deenergized andthe plunger thereof will return to the Fig. 5 position to thereby unlockthe rod 68. unseat the valve member 92, seatv the valve member 08 andclose the switch I61. Air from the atmosphere will then enter valvechamber ll through pipe II and 0 flow into cylinder 86 through theopenings 66.

The springs 15 and 16 will then tend to move the diaphragm 61, rod 60and pawl 65 toward the right of Fig. 5 which action will take place assoon as the frictional load upon the pawl occasioned by the pressure ofthe sides of the slots 42 is sumciently low to permit the springs I5 andII to pull the pawl out of engagement with the slots II. The outwardmovement of the rod 56 will of course open the switch III as aforesaid.In order to effect shift back into overdrive, the car must beaccelerated to a speed greater than 20 miles per hour and theaccelerator pedal released momentarily to permit the pawl to bereengaged as above described. I

It is desired to point out that while vacuum means has been described asthe preferred prime mover means for operating the overdrive pawl 65,other means may be employed such a a hydraulic cylinder or an electricalsolenoid. Various parts of the mechanism shown and described herein maybe changed or omitted without materially altering the operation of thedevice. For example, the solenoid locking function of the plunger rodportion I4 is not absolutely necessary for the successful operation ofthe overdrive nor is it absolutely necessary to have the switche I12 andIll in the control circuit. Other changes and modifications will readilybe apparent to those skilled in the art and we do not wish to limit ourinvention in its broader aspects to any of the parts, combinations andarrangements such as are shown and described for illustrative purposes,the scope of the invention being defined in the claims appended hereto.

We claim:

1. A prime mover unit adapted for operating a transmission shift membercomprising, a vacuum cylinder having a pressure responsive membertherein adapted for connection to said shift member; a control valveoperably associated with said cylinder; a source of vacuum connectedwith said valve; a shiftable valve element in said valve; a solenoidhaving a plunger connected to said shiftable valve element; saidsolenoid plunger being adapted to shift said valve element in responseto energization of said solenoid thereby to admit vacuum to saidcylinder for shifting said shift member and to have a further range ofmovement for engaging said shift member thereby to hold it againstreverse shift.

2. In a servo-motor having a pressure responsive member adapted to bemoved in one direction by fluid pressure and in the opposite directionby spring pressure, an operating member connected with said pressureresponsive member for movement thereby; electromagnetic means carried bysaid motor and including an armature operable to releasably hold saidoperating member in the position to which it is adapted to be moved byfluid pressure movement of said pressure responsive member whereby saidoperating member is retained in the aforesaid position independently ofsaid fluid pressure; pressure fluid controlling valvingv means for saidpressure responsive memher; and a stirrup carried by said armature andstraddling said operating member for mounting said valving means.

3. In a servo-motor, a reciprocable pressure responsive member; anoperating rod connected with said pressure responsive member foroperation thereby; a spring for urging said pressure responsive memberand rod to one position; means including a valve for supplying vacuumfrom a suitable source to said motor for moving said pressure responsivemember and rod to a second position; a solenoid for controlling saidvalve; circuit controlling switch means carried by said servomotor;means including the disposition of said switch means for causing thesame to be-operated to circuit closing position upon operation of saidvalve to vent said motor and means operable in response to movement ofsaid pressure responsive member and rod to said one position foroperating said switch means to circuit opening position; and latch meanscontrolled by said solenoid and operable upon movement of said pressureresponsive member and rod to said second position for retaining said rodin said second position inde-' pendently of said vacuum supply. w

4. As an article of manufacture, a thrust-developing differentialpressure motor unit comprising, an assembly of component casingstructures defining a housing structure for the motor unit,thrust-transmitting means mounted for reciprocatory movement within saidhousing structure and having a terminal portion projecting from saidhousing structure for delivering thrust from said motor unit, adifferential pressure operated member disposed within said housingstructure. means providing an operable connection between said memberand said thrust-transmitting means whereby to effect movement of thismeans in one of its said directions of reciprocatory movement inresponse to differential pressure movement of a said member, a springwithin said housing structure biasing said member in opposition to itssaid diiferential pressure movement whereby to effect return movement ofsaid -thrust-transmitting means in the other of its said directions ofreciprocatory movement, an electromagnet comprising a coil disposedwithin said housing structure and a plunger armature operably associatedwith said coil, said plunger armature having a rod portion extendingcoaxiaily therefrom, and means carr ed by said thrust-transmitting meansfor engagement with an end of said rod portion and so constructed andarranged as to thereby hold said member in its differential pressureoperated position against the biasing influence of said spring andindependently of the operation of differential pressure on said member.

5. As an article of manufacture, a thrust-developing diilerentlalpressure motor unit comprising, an assembly of component casingstructures defining a housing structure for the motor unit,thrust-transmitting means mounted for reciprocatory movement within saidhousing structure and having a terminal portion projecting from one endor said housing structure for delivering thrust from said motor unit, adifferential pressure operated member disposed within said housingstructure, means providing an operable connection between said memberand said thrusttransmitting means whereby to effect movement of thismeans in one of its said directions of reciprocatory movement inresponse to differential pressure movement of said member, a springwithinsaid housing structure biasing said member in opposition to itssaid differential Pressure movement whereby to effect return movement ofsaid thrust-transmitting means in the other of its said directions ofreciprocatory movement, electromagnetically controlled holding meansdisposed within said housing structure and operable when said member isin its differential pressure operated position to hold said memberagainst its said spring-biased return movement independently of theoperation of differential pressure on said member, an electrical switchcarried by said motor unit adjacent the opposite end of said housingstructure from that aforesaid, said switch comprising a contact membermovable between two circuit-controlling positions and having meansbiasing said contact member to one of these two positions, switch oerating means for moving said contact member from its said spring-biasedposition to the other of its said two positions in re- I a portionoftl'e last mentioned movement of said thrus -transm tting means.

6. As an article of manufacture, a thrustdeveloping servo-motor unitcomprising, a casing structure, reciprocatory means comprising a membermounted for differential pressure movement within said casing iructurefrom a first position to a second position thereof and a rod operablyconnected to said member and having a thrust-transmitting end portionfor utilizing thrust developed by the servo-motor unit, a spring biasingsaid member for movement to its said first position, means carried bysaid casing structure and operable to releasably hold said member in itssaid second position against the bias of said spring and independentlyof the action of differential pressure on said member, a circuitcontrolamass ling switch carried by the servo-motor unit and adapted foroperation to effect closed and open positions of said switch, meansbiasing said switch to one of its said positions, and means forcontrolling said switch in response to operation of said reciprocatorymeans comprising a switch operating plunger having a lost-motionoperating relationship with said reciprocatory means and being soconstructed and arranged in relationship with said switch biasing meanssuch that when said member is in one of its said positions then saidbiasing means serves to maintain said switch in one of its saidpositions and such that, when said member moves from its said oneposition toward the other of its said positions, said switch operatingplunger will transmit thrust irom said reciprocatory means to saidswitch thereby to effect operation of said switch to the other of itssaid positions after said member has completed a predetermined portionof its last said movement as accommodated by said lost-motion operatingrelationship.

7. As an article of manufacture, a thrustdeveloping servo-motor unitcomprising, a casing structure, reciprocatory means comprising a membermounted for differential pressure movement within said casing structurefrom a first position to a second position thereof and a rod operablyconnected to said member and having a thrust-transmitting end portionfor utilizing thrust developed by the servo-motor unit, a spring biasingsaid member for movement to its said first position, means carried bysaid casing structure and operable to releasably hold said member in itssaid second position against the bias of said spring and independentlyof the action of differential pressure on said member, a circuitcontrolling switch carried by the servo-motor unit and adapted foroperation to effect closed and open positions of said switch, meansbiasing said switch to one of its said positions, and means forcontrollin said switch in response to operation of said reciprocatorymeans comprising a switch operating plunger having a lost-motionoperating relationship with said reciprocatory means and being soconstructed and arranged in relationship with said switch biasing meanssuch that when said member is in one of its said positions then saidbiasing means serves to maintain said switch in one of its saidpositions and such that, when said member moves from its said oneposition toward the other of its said positions. said switch operatingplunger will transmit thrust from said reciprocatory means to saidswitch thereby to eiIect operation of said switch to the other of itssaid positions after said member has completed a predetermined portionof its last said movement as accommodated by said lostmotion operatingrelationship, said casing structure having an opening through which saidrod projects thereby to dispose said thrust-transmitting end portion toone side of said difl'erential pressure operated member exteriorly ofsaid casing structure, and means for mounting said switch operatingplunger for movement at the other side of said member and coaxially withsaid differential pressure operated member and said rod.

8. As an article of manufacture, a fluid servomotor unit comprising acasing structure; a pressure difierential and spring operated powerelement housed within said casing structure; a rod operably connectedwith said element and adapted to be moved therewith to perform work onexternal mechanism; valve means carried by the 16 motor unit forcontrolling pressure differential operation of said element; a springbiasing said rod and said element in opposition to said diflerentialpressure operation; solenoid means carried by the motor unit andcomprising an armature for controlling operation of said valve means;latch means operable in response to operation of said armature toreleasably hold said element independently of said diflerential pressurein its position of differential pressure operation and against the biasor said spring; switch means carried by said motor unit; and means foreffecting an operation oi said switch means as an incident to movementof said rod to perform work.

CARL A. NERACHER.

WILLIAM '1. DUNN.

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